DESCRIPTION: (Applicant's Description) There has been a dramatic increase in the use of transition metal catalysts in organic synthesis. Most of these processes depend on the availability of catalysts to perform specific transformations that allow for a new array of bond constructions. One of the advantages of organometallic catalytic processes is the ability to tune the activity and selectivity by the modification of the ligands around a metal reaction center. Olefin methathesis has provided a new way of constructing carbon-carbon double bonds that has seen an explosion of new uses over the past few years. This new usage has resulted from the development of a family of easy to prepare catalysts that are robust and can be used under normal organic conditions. Key to the development of these catalysts has been the ability to design and control the ligand environment to regulate the reactivity and open new reaction modes. The present proposal builds on the past work in our group that has produced the work horse catalysts for majority of the applications in organic synthesis. By the appropriate modification of ligands, these catalysts have developed from ill-defined catalysts with low activity to a new generation of systems that open a wide variety of new applications. A part of this proposal will be directed toward the exploitation of a new family of catalysts that allow for the metathesis of olefins containing electron-withdrawing groups. The majority of the present proposal will focus on the development of new catalysts that allow for the stereoselective synthesis of olefins. The goal is to develop the catalysts and surrounding technology that allows high Z or E olefins to be prepared from simple starting materials by catalytic processes. The catalyst will control the stereochemistry of the resulting double bond, not the substrate. In a related way, catalysts that will allow the kinetic resolution of dienes to be performed to give products of high e.e. will be developed. Ligands that are easily prepared will be used in catalytic systems that can be used under normal organic conditions. This research is directed toward the development of strategies and catalysts that will make the olefin metathesis reaction the method of choice for the stereoselective synthesis of olefins and polyenes.